Sensitive periods are defined as a time in development during which the brain is particularly responsive to experiences in the form of patterns of activity (Daw, 1997).This time point may be termed a critical period if the presence or absence of an experience results in irreversible change (Newport, Hindle, & Jackson, 2001; Trachtenberg & Stryker, 2001). Those factors that allow a circuit underlying development to be plastic - or render it unchangeable - are becoming increasingly well understood in a small number of domains (i.e., visual and perceptual development). However, there is a paucity of data on sensitive periods for normative social and emotional development in human infants and children and little is known about the effects of aberrant experiences during early development on the emergence of psychopathology. The case of infants abandoned since birth into institutions provides an opportunity to examine the effects of severe psychosocial deprivation and sensitive periods in typical neural, social-emotional and cognitive development, as well as in trajectories that lead to psychopathology. Over the past 10 years we have conducted just such a study in which infants, abandoned since birth and raised in institutions in Bucharest, Romania, were randomly assigned either to be removed from the institution and placed into a family/foster care intervention or to be left in the institutions to care as usual. These children have been followed through 8 years of age and thus far, the data through 54 months of age indicate that a) early institutionalization leads to perturbations in brain electrical activity, profound deficits and delays in cognitive and socio- emotional behaviors, and a greatly elevated incidence of psychiatric disorders and impairment, b) our intervention was broadly effective in enhancing children's development, but c) for specific domains of neural activity, language, cognition and social-emotional functioning there appear to be sensitive periods regulating recovery. In the current proposal, we will extend these analyses with the aim to predict mental health outcomes in two groups of children: those originally assigned to our Foster Care intervention [FCG] and those originally randomized to remain in the institution (Care as Usual Group [CAUG] when they are 12 years of age, and we will compare their functioning to typically developing age-matched Romanian children (Never Institutionalized Group [NIG]). Using both brain (EEG/ERP) and behavioral measures, we propose to 1) reexamine, at age 12, the long term impact of early institutionalization on mental health outcomes and the efficacy of our intervention in ameliorating the burden of mental health outcomes using an intent-to-treat design; 2) examine how the dose of institutionalization (percent time spent in an institution) influences long term outcomes; and 3) examine sensitive periods in recovery from early institutionalization.